Just an observation...
When a fish is not feeling well, it's hard to get them to eat. Therefore, it's hard to get dewormers into them. I realize you can dose Prazi as a bath, but it may not hit the parasites you're worried about. I believe that Panacur only works when dosed with food.
IME, fishes can live with quite a load of internal parasites without any major problems. I think that the formalin bath is a good idea. It might kill some/most "active" parasites that are stressing the fish out. Then maybe they'll eat. And in my personal experience, clownfishes tolerate freshwater dips quite well. I've had them go for over an hour without any major signs of stress. It would help to rid them of possible trematodes (possibly the root of gill issues). Formalin baths would help with protozoans/fungus/bacterium. Hyposalinity works well for Cryp, buy opens you up to a major problem with Uronema.
Unfortunately, with new arrivals, we have very little information to go on. You have to go with what you've got. Not everyone has a microscope at home to examine smears/scrapes with. And honestly, I don't expect them to. Treating with something very broad-spectrum and low lethality is not harmful IMO.
Getting rid of the major stressors will perk up appetite...and then you can deal with internal parasites. It's kind of like a triage. Deal with your most pressing problems first...then work from there.
Sorry, I just think that too often, people focus on secondary problems first...